The control and/or elimination of undesirable impurities and by-products from various manufacturing operations has gained considerable importance in view of the potential pollution such impurities and by-products may generate. One conventional approach for eliminating or at least reducing these pollutants is by oxidizing them via incineration. Incineration occurs when contaminated air containing sufficient oxygen is heated to a temperature high enough and for a sufficient length of time to convert the undesired compounds into harmless gases such as carbon dioxide and water vapor.
In view of the high cost of the fuel necessary to generate the required heat for incineration, it is advantageous to recover as much of the heat as possible. To that end, U.S. Pat. No. 3,870,474 discloses a thermal regenerative oxidizer comprising three regenerators, two of which are in operation at any given time while the third receives a small purge of purified air to force out any untreated or contaminated air therefrom and discharges it into a combustion chamber where the contaminants are oxidized. Upon completion of a first cycle, the flow of contaminated air is reversed through the regenerator from which the purified air was previously discharged, in order to preheat the contaminated air during passage through the regenerator prior to its introduction into the combustion chamber. In this way, heat recovery is achieved.
U.S. Pat. No. 3,895,918 discloses a thermal regeneration system in which a plurality of spaced, non-parallel heat-exchange beds are disposed toward the periphery of a central, high-temperature combustion chamber. Each heat-exchange bed is filled with heat-exchanging ceramic elements. Exhaust gases from industrial processes are supplied to an inlet duct, which distributes the gases to selected heat-exchange sections depending upon whether an inlet valve to a given section is open or closed.
Various valving systems have been disclosed in the art for such regeneration incinerators. For example, U.S. Pat. No. 4,658,853 discloses a butterfly-type valve subassembly positioned in an incineration system duct communicating with a source of gaseous effluents and at least one heat-exchange section. The subassembly has a planar member with at least one peripheral groove formed on at least one principal surface thereof. In the nominally closed valve position, the groove or grooves are positioned to be in communication with grooves in corresponding valve seat members inside the subassembly housing. The grooves are the terminations of passageways that are adapted to be coupled to sources of pressurized gases for preventing the flow of gases past the planar member when the valve is nominally closed.
Similarly, U.S. Pat. No. 4,252,070 discloses a double valve anti-leak system for thermal regeneration incinerators wherein double valves are provided in series at the inlet and/or outlet to each heat-exchange section. Leakage is minimized by using inlet and exhaust valves in sets of two, which produces a double pressure drop across them so that there is a lessened negative pressure produced by the exhaust fan, and therefore a lesser probability of leakage. However, this approach requires the use of twice the typical double number of valves and appurtenant controls.
U.S. Pat. No. 5,000,422 discloses a leakage control system that conducts leakage back to an incinerator for oxidation or provides a pressure differential that precludes leakage of emissions past the control valves. A circular butterfly valve is provided that is rotatable about an axis extending diametrically of a cylindrical valve housing. The butterfly has two axially spaced seal surfaces on the periphery that, in conjunction with complementary axially spaced seats on the valve housing, control the flow of air to or from an annular plenum that surrounds the valve housing.
U.S. Pat. No. 4,280,416 discloses a rotary valve for controlling the flow of gases in a regenerative thermal reactor. Slots formed on a rotating plate allow communication of the purging, exhaust and inlet ducts with selective heat-exchange chambers.
It would be desirable to provide suitable valving for thermal oxidizers and the like that are economical to manufacture, easy to control, result in minimal or no leakage, and exhibit fast response times.
It is therefore an object of the present invention to provide valving to minimize or prevent leakage of unpurified effluent across the valves in thermal oxidizers.
It is a further object of the present invention to provide thermal oxidizer apparatus valving to minimize or prevent leakage of unpurified effluent across the valves in an economically efficient manner.
It is a still further object of the present invention to provide quick actuation valving in thermal oxidizer apparatus while minimizing or preventing leakage of unpurified effluent across the valves.
It is an even further object of the present invention to provide a consolidated poppet valve housing in modular format to allow for additional valve housings to be added to handle increased flow loads.
It is yet a still further object of the present invention to provide a consolidated poppet valve housing that reduces the necessary duct work for communication from the process gas source and to the regenerative thermal oxidizer apparatus.